Sampler for liquid chromatography

ABSTRACT

A sampler for liquid chromatography is described. The sampler includes an injection valve and a sample loop. The injection valve includes one waste port, two sample loop ports, and two high-pressure ports. The sample loop port includes a first loop part and a second loop part. The injection valve can be configured to have LOAD position and INJECT position. The injection valve can also be configured to have one or more additional positions such as a FULL PURGE position, a PUMP PURGE position, and a NEGATIVE PRESSURE position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is Continuation under U.S.C. § 120 and claims thepriority benefit of co-pending U.S. application Ser. No.15/190,529[Attorney Docket Number TP20036US1-NAT], filed on Jun. 23,2016, which claims the priority benefit under 35 U.S.C. § 119 to GermanPatent Application No. DE 10 2015 110 254.4 [Attorney Docket NumberTP20036DE1/NAT], filed on Jun. 25, 2015, the disclosure of which isincorporated herein by reference.

FIELD OF INVENTION

The present invention relates to a sampler for liquid chromatography, inparticular for high performance liquid chromatography (HPLC), whichsampler has an injection valve with an extremely low leakage rate andalso permits the cleaning of the ports and of the grooves of theinjection valve, of the sample loop, of the sample delivery device, ofthe injection needle and of the needle seat exclusively by way of thesolvent pump(s).

BACKGROUND

In HPLC, a sample to be examined must be fed into a high-pressure liquidflow, wherein the latter must be interrupted only for as short a periodof time as possible. For this purpose, high-pressure injection valvesare used which permit a virtually interruption-free switch of the liquidflow. Such a design is described for example in U.S. Pat. No. 3,530,721A.

Injection valves used at present have at least four ports in order topermit sample pre-compression by way of a sample delivery device. Anadditional port is required if it is sought to dispose of solventcontained in the sample delivery device, or of an incorrectly taken-insample, via a waste port (disposal port) connected to the injectionvalve. A sampler having a corresponding injection valve is alreadydescribed in DE 10 2008 006 266 A1.

During a change of the solvent in an HPLC system, it is necessary forold solvent in the lines between the solvent bottles and the injectionvalve to likewise be flushed out via the waste port. Here, it is forexample possible for the so-called injection needle to be moved directlyover a waste container and for the contents of the line to be disposedof by way of the solvent pump(s). The disposal is generally referred toas “purge”. The abovementioned solvent change is described for examplein U.S. Pat. No. 6,129,840 A.

If it is however sought to clean not only the sample delivery device butalso the so-called needle seat, use is made, in known solutions, of asecond solvent pump for cleaning purposes, as described for example inUS 2013067997 A1.

In the prior art, therefore, only the lines from the solvent drawing-inlines to the switching valve, including the sample delivery device andthe injection needle, but not the needle seat itself, are flushedthrough by means of the solvent pump(s). A further cleaning pump isconsequently required for this purpose. Owing to the further pump, theconstruction becomes more complex and more expensive. If a further pumpis omitted, contaminants in the needle seat must be accepted, whichresult in a so-called carry-over between the individually analyzedsamples.

In the prior art, for the realization of the sample pre-compression andsample decompression, for the taking-in of the sample, for the sampleinjection and for the so-called purging, at least 3 grooves are providedin the stator or in the rotor of the injection valve in order to make itpossible for corresponding switching positions to be realized. This hasthe result that the sealing surface between the connections becomes verysmall, leading to certain leakage rates. It would accordingly beadvantageous to provide an injection valve which, by means of at most 2grooves, makes it possible to realize all of the required switchingstates.

Furthermore, in the so-called injection position (INJECT position) ofthe injection valve, that is to say the position while the sample istransferred to the chromatography column, some connecting lines of asampler are not fully flushed through. Most connections, formed in themanner of grooves in the stator or rotor of the injection valve, arerequired in order to be able to switch back and forth between theso-called loading position (LOAD position; introduction of the sampleinto a sample loop of the injection valve) and the pressure equalizationposition (PRESSURE EQUALIZATION position; position in which the sampleloop is brought to the system pressure or ambient pressure), and alsobetween the INJECT position and the PRESSURE EQUALIZATION position,without the solvent flow to the column being interrupted. The flow mustnot be interrupted because, otherwise, the pump pressure would rise toan extreme extent and the column pressure would drop. The former is aproblem for safety reasons, and in the case of the latter, longequilibration phases are required between the sample analyses. Thesolvent used at the start of the chromatography run (for example in theequilibration phase) accumulates in said grooves and falsifies thegradient composition during the further process owing to the mixing ofthe solvent residue with the gradient (which is critical in particularin the case of low-flow/nano-flow applications).

SUMMARY

It is therefore the object of the present invention to provide aninjection valve of a sampler, which injection valve is of simpleconstruction, makes do with a small number of ports and groovesconnecting the ports, has no cleaning pump, exhibits a more intensesealing action, and has no regions that are not flushed through, andwhich can furthermore be produced inexpensively, wherein differentswitching positions of the injection valve should be made possible, suchas pressure equalization position, position for receiving the sample,positions for sample injection and for purging the lines from thesolvent bottles to the switching valve, with or without sample deliverydevice, and needle and needle seat, and also a position for producing anegative pressure.

The invention achieves the stated object through the provision of asampler for liquid chromatography, in particular high performance liquidchromatography, (a) having an actuable injection valve which has atleast one waste port for the discharge of fluid at low pressure, a firstand a second sample loop port, and two high-pressure ports for thesupply and discharge of fluid at high pressure, one high-pressure portbeing connectable to a pump and the other high-pressure port beingconnectable to a chromatography column, (b) having a sample loop, (i)which sample loop comprises a first sample loop part which is connectedat one end to the first sample loop port and at the other end to a pumpvolume of a sample delivery device, (ii) which sample loop comprises asecond sample loop part which is connected at one end to the secondsample loop port and at the other end to the pump volume of the sampledelivery device, (iii) the second sample loop part being formed suchthat it can be divided into a drawing-in part and a supply part, and(iv) it being possible, in the divided state, for a sample fluid to bedrawn in by means of the free end of the drawing-in part connected tothe pump volume, which sample fluid can, in the connected state, besupplied via the supply part in the direction of the first sample loopport, and (c) the injection valve being designed (i) such that, in aLOAD position, the two high-pressure ports are connected to one another,and that sample loop port which is connected to the second sample looppart is connected to the waste port, and (ii) such that, in an INJECTposition, that high-pressure port which is connectable to the pump isconnected to the second sample loop port, and that high-pressure portwhich is connectable to the chromatography column is connected to thefirst sample loop port, wherein (d1) the injection valve has a FULLPURGE position, in which the second sample loop port is connected to thewaste port, and that high-pressure port which is connected to the pumpis connected to the first sample loop port, and/or (d2) the injectionvalve has a PUMP PURGE position in which the second sample loop port isconnected to that high-pressure port which is connectable to thechromatography column, and that high-pressure port which is connectableto the pump is connected to the waste port, and/or (d3) the injectionvalve has a NEGATIVE PRESSURE position in which that high-pressure portwhich is connectable to the pump is connected to the first sample loopport, and the second sample loop port is sealingly closed.

The feature (d1) has the advantage that both the sample loop and thehigh-pressure port connected to the pump, the two sample loop ports, thewaste port and the sample delivery device can be flushed through by wayof the solvent pump (hereinafter referred to merely as “pump”), withoutit being necessary for the sampler to have a further cleaning pump. Thefeature (d2) has the advantage that the injection valve can also have aposition in which the port connected to the high-pressure pump and thewaste port can be flushed through. In the PUMP PURGE position, thatsample loop port which is connected to the second sample loop part ispreferably sealingly closed off. According to the invention, therefore,the expression FULL PURGE is to be understood to mean a state in whichall of the grooves and ports of the injection valve (with the exceptionof that high-pressure port which is connectable to the chromatographycolumn) and all of the supply and discharge lines, sample loops and thesample delivery device can be flushed through with solvent, and therebycleaned, preferably by way of a pump. Furthermore, in the FULL PURGEposition of the injection valve, it is also possible for the sampleneedle, from the outside, and the injection port to be washed. For thispurpose, the sample needle is moved away from the needle seat (alsoreferred to as injection port) slightly in order that the solventdelivered by the pump washes away contaminants on the outer side of thesample needle and on the needle seat. The contaminated solvent can thenflow, for example via an overflow on the needle seat, into a wastevessel. According to the invention, the expression PUMP PURGE is to beunderstood to mean a state in which the supply line from the pump to thehigh-pressure port connected thereto, said high-pressure port itself,the connecting groove between said high-pressure port and the wasteport, and the waste port itself can be flushed through with solvent andthereby cleaned, and also, solvent can be disposed of. The feature (d3)has the advantage that, in said position, it is possible for a negativepressure to be produced in the sample loop 51, 44, 52 and as far as thepump. Said negative pressure can be produced by virtue of the pumpvolume of the sample delivery device being increased, preferably byvirtue of a movable element (piston) of the sample delivery device beingmoved outward. The production of the negative pressure makes it possiblefor the pump to assist in the drawing-in of the solvent, by virtue ofthe hydrostatic column of the solvent in the solvent bottles beingovercome. Furthermore, the NEGATIVE PRESSURE position makes it possiblefor undesired gas bubbles in the device to be increased in size, suchthat they can be more easily removed from said device.

A further advantage of the valve construction of the sampler accordingto the invention lies in the fact that, depending on the switchingposition of the injection valve, it is possible for virtually all of theprovided parts to be flushed through by way of the solvent pump(s). Itis thus furthermore preferable for the sampler according to theinvention to have at most one (solvent) pump path. Here, the pump pathis to be understood to mean the connecting line from the solvent pump(s)to the corresponding high-pressure port. The sampler according to theinvention may thus comprise not only one solvent pump but even two ormore solvent pumps, which can all supply solvent via the correspondinghigh-pressure port. According to the invention, it is preferable if thesampler has no further cleaning pump in addition to the one or moresolvent pump(s), because, owing to the different switching positions ofthe injection valve, the cleaning can be performed by way of solventdelivered by the one or more solvent pump(s).

In a further preferred embodiment of the invention, the injection valveof the sampler according to the invention may also, as possiblesettings, have the FULL PURGE position and the PUMP PURGE position, orthe FULL PURGE position and the NEGATIVE PRESSURE position, or the PUMPPURGE position and the NEGATIVE PRESSURE position, or all threepositions together.

In a further embodiment of the sampler according to the invention, thathigh-pressure port to which the column is connected is sealingly closedwhen the injection valve is in the FULL PURGE position. The same appliesto the first sample loop port in the PUMP PURGE position and to thesecond sample loop port in the NEGATIVE PRESSURE position.

In a further embodiment of the sampler according to the invention, theinjection valve has a PRESSURE EQUALIZATION position, in which the firstand the second sample loop ports of the closed sample loop do not have aconnection to the other ports, that is to say to the two high-pressureports and to the waste port of the injection valve. Here, it isfurthermore preferable if, in the PRESSURE EQUALIZATION position, thetwo high-pressure ports are connected to one another.

It is furthermore preferable if the injection valve of the sampleraccording to the invention has at most 5 ports, specifically the twosample loop ports, the two high-pressure ports and the waste port. Thereduction to a maximum of 5 ports simplifies the construction of thesampler and reduces the leakage rate in relation to an injection valvewith 6 or more ports.

It is furthermore preferable according to the invention if thathigh-pressure port which is connected to the pump(s) is spaced apartfrom the two sample loop ports, from the waste port, and from thathigh-pressure port which is connected to the chromatography column, byin each case substantially the same distance. The expression“substantially” is intended to clarify that, here, merelymachining-induced differences in spacing may exist, which however do notinfluence the functionality of the injection valve. It is furthermorealso preferable if the sample loop ports are situated on opposite sideswith respect to that high-pressure port which is connected to thepump(s), and the two sample loop ports are spaced apart from the wasteport, and from that high-pressure port which is connected to thechromatography column, by in each case substantially the same distance.In this case, too, the expression “substantially” is intended to havethe meaning as given above.

Said spacings of the various ports in the two above-mentioned preferredembodiments run within a direction of extent of the contact surface of arotor and of a stator of the injection valve.

Thus, in a further embodiment of the sampler according to the invention,it is preferable if the injection valve has a rotor and a stator, therotor having a face surface which interacts with the face surface of thestator (contact surface of stator and rotor) and in which there areformed (at least) two grooves by means of which, in a manner dependenton the rotational position of the rotor relative to the stator, portopening cross sections of the two high-pressure ports, of the two sampleloop ports and of the waste port provided in the face surface of thestator are connected in pressure-tight fashion or are shut off inpressure-tight fashion. It is furthermore preferable for one groove ofthe (at least) two grooves, which groove connects the two high-pressureports in the LOAD position of the injection valve, to be designed suchthat it still connects the high-pressure ports even after a rotation ofthe stator relative to the rotor into the PRESSURE EQUALIZATIONposition.

It is possible according to the invention for the injection valve toalso have more than two grooves. However, according to the invention, itis particularly preferable for the injection valve to have at most thetwo stated grooves, in particular in order to realize all of the statedpositions of the injection valve. The number of at most two grooves hasthe advantage that the leakage rate in the injection valve can be keptvery low.

One of the grooves, said groove connecting the two high-pressure portswhen the injection valve is in the LOAD position, is preferably ofhook-shaped form, and the other of the grooves, said groove connectingthe first sample loop port to the waste port when the injection valve isin the LOAD position, is preferably of arcuate form. The two groovespreferably run in the direction of the interacting face surfaces of therotor and of the stator. The expression “arcuate” is to be understood tomean that the profile of said groove runs over a circular segmentaround, as a central point, that high-pressure port which is connectedto the pump(s). The so-called hook-shaped groove is preferably formedsuch that, as a result of rotation of the stator and of the rotorrelative to one another during a change from the LOAD position into thePRESSURE EQUALIZATION position, a partial extent of the hook permits aconnection of said groove to that high-pressure port which is connectedto the chromatography column.

Said designs of the grooves and ports in the injection valve of thesampler according to the invention have the advantage that, in virtuallyall switching positions (with the exception of PRESSURE EQUALIZATIONposition and NEGATIVE PRESSURE position), all parts of the grooves andports can be flushed through. In other words, there is virtually noregion in the injection valve which cannot be flushed through, such thatgood cleaning is possible, and no contamination-induced changes inoperational behavior occur during HPLC operation.

It is furthermore preferable according to the invention if the injectionvalve has, at most, the stated six positions, specifically the LOADposition, the PRESSURE EQUALIZATION position, the INJECT position, thePUMP PURGE position, the FULL PURGE position and the NEGATIVE PRESSUREposition, preferably in order to be able to realize all required statesin a sampler for HPLC. According to the invention, all of the statedpositions can be realized by way of the two abovementioned grooves inthe injection valve.

The injection valve of the sampler according to the invention ispreferably constructed such that, by rotation, it can be transferredinto the following positions in the stated sequence: LOADposition->PRESSURE EQUALIZATION position->INJECT position->PUMP PURGEposition->FULL PURGE position->NEGATIVE PRESSURE position->LOADposition. This has the advantage that the transitions from therespective switching position into the respectively required subsequentswitching position are possible directly and without undesiredintermediate switching positions. In this way, there are no samplelosses, no undesired mixing with any residues in ports that wouldotherwise come into contact owing to intermediate switching positions,and no undesired pressure drop.

Furthermore, the sampler according to the invention preferably has acontrol unit for controlling the injection valve and the sample deliverydevice.

The sample delivery device may preferably also have a movable elementwhich is guided in sealed fashion in a pump volume and which can bemoved by way of a drive, which can be actuated by the control unit, ofthe sample delivery device for the purposes of delivering the samplefluid contained in the pump volume.

The sample delivery device is preferably of high-pressure-resistant formand can generate pressures which are used in high performance liquidchromatography, preferably pressures of greater than 500 to 600 bar,most preferably pressures of greater than 1500 bar.

The sampler according to the invention has the advantage that theintegration of a sample delivery device into the split loop arrangementmakes it possible to realize pressure equalization by way of the sampledelivery device during the change of switching positions of theinjection valve if the injection valve has, for this purpose, a PRESSUREEQUALIZATION position in which those sample loop ports of the injectionvalve which are connected to the ends of the sample loop are notconnected in the injection valve to other ports.

In the case of the split loop principle, the sample loop is divided inthe connecting part between the sample delivery device, which may forexample be in the form of a syringe, and the respective sample loop portof the injection valve. The end of the drawing-in part, connected to thesample delivery device, of the divided connecting part of the sampleloop is, for the purposes of drawing in the required sample volume ordrawing in a flushing medium, moved to a sample vessel or to a vesselfor the flushing medium. Subsequently, the divided connecting part ofthe sample loop is connected again, such that the drawn in sample volumecan, in the INJECT position of the injection valve, be injected into thechromatography column by means of the pump(s). This basic principle hasalready been described in U.S. Pat. No. 4,939,943 A1.

According to the invention, the injection valve is, after the drawing-inof the volume in the LOAD position, switched into the PRESSUREEQUALIZATION position in which the sample loop ports are shut off inpressure-tight fashion. In the PRESSURE EQUALIZATION position, the driveof the sample delivery device is preferably actuated such that, in theclosed sample loop and in the pump volume of the pump delivery device, apressure builds up which substantially corresponds to the systempressure. Even if the pressure in the sample loop before the switchingof the injection valve from the PRESSURE EQUALIZATION position into theINJECT position is not identical to the system pressure of the pump(s),but a slight pressure difference still remains, said small pressuredifference is, according to the invention, kept so low that the pressuredifference cannot inadmissibly have an adverse effect on the flowthrough the chromatography column or even lead to damage to theinjection valve or to the chromatography column.

The same applies analogously for the switching from the INJECT positioninto the LOAD position. Here, too, a switch is initially made from theINJECT position into the PRESSURE EQUALIZATION position, in which areduction of the pressure, which corresponds substantially to the systempressure, is performed until substantially the ambient pressure isreached. Here, too, it may be the case that a small, non-problematicpressure difference remains when a switch is made from the PRESSUREEQUALIZATION position into the LOAD position.

The pressure equalization (pressure increase or pressure decrease) inthe sample loop is, according to the invention, preferably realizedthrough corresponding actuation of the drive of the sample deliverydevice. In this way, no disruptive fluid flows arise during the pressureequalization.

In one preferred embodiment of the invention, in the PRESSUREEQUALIZATION position of the injection valve, the two high-pressureports are connected. In this way, the flow of the fluid through thechromatography column is maintained, and during the switching processes,no undesired peaks in the pressure profile can occur.

Said movable element in the sample delivery device may for example be inthe form of a driven syringe, wherein the movable element is formed bythe piston of the syringe.

It may be provided that, after the PRESSURE EQUALIZATION position of theinjection valve is reached, the control unit, by a correspondingactuation of the drive, moves the piston or the movable element by apredetermined travel which suffices to generate a change in the pumpvolume of the sample delivery device as necessitated by elasticities ofthe devices which conduct the fluid and by the compressibility of thefluid itself, wherein a pressure reduction in the sample loopsubstantially to ambient pressure can be achieved by means of anincrease in size of the pump volume, and a pressure increase in thesample loop substantially to the working pressure of the pump(s) can beachieved by means of a reduction in size of the pump volume. Themovement of the movable element may be performed in controlled orregulated fashion.

To permit regulation of the pressure or final pressure during thepressure equalization in the sample loop, a pressure sensor may beprovided which detects the pressure of the fluid in the closed sampleloop or in the pump volume of the sample delivery device, at leastduring the time in which the injection valve is situated in the PRESSUREEQUALIZATION position.

In this variant, the signal of the pressure sensor is preferablysupplied to the control unit, wherein the control unit compares thepressure of the fluid with a pressure setpoint value and actuates thesample delivery device such that the pressure of the fluid reaches ahigh pressure setpoint value before the switching of the injection valvefrom the PRESSURE EQUALIZATION position into the INJECT position, and/orsuch that the pressure of the fluid reaches a low pressure setpointvalue before the switching of the injection valve from the PRESSUREEQUALIZATION position into the LOAD position.

In a further embodiment of the present invention, the sampler accordingto the invention preferably has a waste line which leads from the wasteport into a vessel surrounding the needle seat or into the needle seatitself. According to the invention, said needle seat has a washingfunction. If, in the FULL PURGE position, the sample needle is moved outof the needle seat slightly, the delivered solvent can wash over thesample needle from the outside. Here, the needle seat with washingfunction preferably has an overflow from which the solvent can flow offinto a waste vessel.

The present invention also relates to the use of a sampler according tothe invention in liquid chromatography, in particular in highperformance liquid chromatography. In other words, the present inventionrelates to a method for performing liquid chromatography using a sampleraccording to the invention, in particular by switching of the positionsof the injection valve of the sampler according to the invention in themanner specified above. It is preferable if, during the use of thesampler according to the invention, the pump(s) for delivering thesolvent/fluid are/is also used as cleaning pump(s), in particular in thePUMP PURGE position and in the FULL PURGE position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be discussed in more detail below on the basis of anexemplary embodiment illustrated in the drawings.

FIG. 1 is a schematic illustration of an HPLC system having a sampleraccording to the invention, to which a chromatography column isconnected, wherein the injection valve is situated in the LOAD position.

FIG. 2 shows the HPLC system in FIG. 1, wherein the injection valve hasbeen switched from the LOAD position into the PRESSURE EQUALIZATIONposition.

FIG. 3 shows the HPLC system from FIGS. 1 and 2, which has been switchedinto the INJECT position.

FIG. 4 shows the HPLC system from the preceding figures, wherein theinjection valve has been switched into the PUMP PURGE position.

FIG. 5 shows the HPLC system from the preceding figures, wherein theinjection valve has been switched into the FULL PURGE position.

FIG. 6 shows the HPLC system from the preceding figures, wherein theinjection valve has been switched into the NEGATIVE PRESSURE position.

FIG. 7 shows the HPLC system from FIG. 5 in the FULL PURGE position withadditional connecting line from the waste port into the wash port of theneedle seat.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows, in a schematic illustration, an HPLC system having asampler 10 which operates on the basis of the split loop principle andwhich has a sample delivery device 5, an injection valve 3 and a pump,preferably high-pressure pump 40. Furthermore, the sampler 10 has asample loop which is composed of the first connecting part 51 and of asecond connecting part 52, 44. This may be a pressure-resistant linewith a small diameter, for example in the form of glass or high-gradesteel capillaries. The connecting part 51 is connected to a first sampleloop port 16 of the injection valve 3 and to the sample delivery device5, or to the pump volume V thereof. The second connecting part, which iscomposed of a drawing-in part 44 and a supply part 52, is designed suchthat it can be divided. For this purpose, the supply part 52 issues intoan injection port 45 which is connected via the supply part 52 to asecond sample loop port 13 of the injection valve 3. The drawing-in part44, which at one end is connected to the pump volume V of the sampledelivery device 5, has at the other end a sample needle 42 by way ofwhich the drawing-in part 44 can be connected to the injection port 45.

The sample needle 42 can however also be moved to a sample vessel 43 andcan, in the manner discussed below, draw a defined sample volume fromsaid sample vessel into the drawing-in part 44. Furthermore, the sampleneedle 42 can also be moved to a vessel for a cleaning fluid (notillustrated) in order to draw cleaning liquid from the latter into thesample delivery device 5. When the sample needle 42 is placed into theneedle seat 45 again, owing to the fact that the port 13 is closed offin pressure-tight fashion (FIG. 4), it is possible, as the piston 53 ispushed downward, for the received cleaning fluid to be transported tothe chromatography column via the sample loop part 51, the port 16, thegroove 23 and that port 14 which is connected to the chromatographycolumn 41. In this way, the chromatography column 41 can be cleaned.This cleaning procedure is preferably performed in the PUMP PURGEposition of the injection valve, which is illustrated in FIG. 4.

In the illustrated embodiment, the sample delivery device 5 comprises asyringe 50 in which a piston 53 is guided in pressure-tight anddisplaceable fashion. The piston 53 is driven by means of a drive 55,for example a stepper motor. The drive is preferably actuated by acontrol unit (not illustrated). The control unit preferably alsocontrols the switching processes of the injection valve 3, which has anactuable drive (not illustrated).

A waste port 12 of the injection valve is preferably connected to awaste line 47 from which a fluid can be discharged into a wastereservoir (not illustrated).

The high-pressure pump(s) 40 are/is connectable to a high-pressure port15 of the injection valve 3. A chromatography column 41 is connectableto the further high-pressure port 14. The high-pressure pump(s) 40 maybe integrated, as constituent parts, into the sampler, though may alsobe provided in some other unit or in a separate pump unit.

The injection valve 3 is preferably composed of a stator 1 and of arotor 2. Here, the stator 1 preferably has the two high-pressure ports14 and 15, the two sample loop ports 13 and 16 and the waste port 12. Byway of said ports, the injection valve 3 is connected via theabove-described connecting lines, which may be in the form of capillaryconnections, to the other functional elements of the HPLC system. Thehigh-pressure screw connections required for this purpose are notillustrated in FIG. 1 for the sake of clarity. For simplicity, theinjection valve is illustrated at the boundary surface between thestator 1 and rotor 2, wherein both the design of the face surface of thestator 1 and the design of the face surface of the rotor 2 are shown inorder to facilitate understanding of the mode of operation. Within theinjection valve 3, the ports are preferably in the form of bores whichlead to the other side of the stator 1. In FIG. 1, the rotor 2 has theat least 2 grooves 23 and 25, which are aligned precisely with the boresof the inlet and outlet ports.

The rotor 2 is preferably pressed with a contact pressure force againstthe stator, such that a common interface forms between rotor 1 andstator 2, at which interface the two parts are sealed against oneanother. The contact pressure force is in this case configured such thatthe arrangement remains sealed even in the presence of the highestpressures to be expected.

In the LOAD position of the valve 3, as shown in FIG. 1, the grooves 23and 25 are aligned with the ports 12-16 such that the groove 23 connectsthe sample loop port 13 to the waste port 12 and the groove 25 connectsthe two high-pressure ports 14 and 15. In this LOAD position, thehigh-pressure pump(s) 40 can thus convey fluid in the direction of thechromatography column 41. Here, the sample loop port 16 is preferablyclosed in pressure-tight fashion. In this LOAD position, it isfurthermore possible for the sample to be taken in from a sample vessel43. For this purpose, it is possible for the sample needle 42 to bemoved into a sample vessel. There, by way of movements of the piston 53upward, that is to say out of the sample delivery device, for examplefrom the position A into the position C (see FIG. 1), the sample can bedrawn from the sample vessel into the sample needle 42 and possibly alsointo the sample loop 44. Then, the sample needle 42 can be moved fromthe sample vessel 43 into the injection port, for the purposes ofinjection after pressure equalization has taken place.

In a next step, the pressure in the sample loop is brought into linewith the system pressure of the chromatography column 41, that is to saywith the pressure with which the high-pressure pump(s) 40supplies/supplies fluid to the inlet of the chromatography column 41.For this purpose, the injection valve is firstly switched into aPRESSURE EQUALIZATION position in which the connecting part 51 and thesecond connecting part or the supply part 52 of the sample looppreferably do not have any connection to the other ports of theinjection valve (FIG. 2).

To adapt the pressure in the sample loop 52, 44, 51 including the sampledelivery device 5 to the system pressure, it is possible for the piston53 of the high-pressure-resistant sample delivery device 5 to be movedfrom the position C into position B. So as not to interrupt the flowthrough the chromatography column 41 during the delivery of the volumerequired for the compression of the sample loop content, the groove 25in the rotor 2 is preferably of hook-shaped form such that, even in thePRESSURE EQUALIZATION position, the two high-pressure ports 14 and 15are still connected. The delivery travel of the piston 53 from positionC to position B, such as is required for the build-up of pressure, canbe calculated from the compressibility of the fluid volume enclosed inthe sample delivery device 5 and sample loop, from the elasticity of thearrangement, and from the present pump pressure. Alternatively, thepressure equalization may be achieved by way of a regulation loop forthe pressure in the high-pressure-resistant sample delivery device. Forthis purpose, the pressure must be measured at a suitable location, andthe position of the piston 53 in the sample delivery device 5 must beadjusted by means of the drive 55 such that the pressure corresponds tothe required target pressure (=column pressure). For the pressuremeasurement, use may be made of a pressure sensor, or indirectly, aforce measurement. A force measurement at the piston 53 or in the drive55 are conceivable solutions. After pressure equilibrium has beenachieved, the valve is switched into an INJECT position, and in thisway, the drawn-in sample volume is injected into the column 41 (FIG. 3).The delivery of the sample volume to the column is preferably realizedby way of the pump flow, specifically via the sample loop part 52, thesample loop port 13, the groove 23 and the high-pressure port 14.

A control unit (not illustrated) can detect the force that the drive 55must impart in order to achieve a corresponding compression in thesample loop. For this purpose, the drive 55 may have an integratedsensor (not illustrated), the signal of which is supplied to the controlunit. In this way, the control unit can determine the actual pressure inthe pump volume and thus in the sample loop (the pressure drop in theconnecting parts and in the valve is negligibly small) and regulate saidactual pressure to the desired value.

After the drawn-in sample volume has been delivered entirely from thedrawing-in part 44 to the column 41 by way of the fluid delivered by thepump(s) 40, the valve can, for the decompression of the sample loop, beswitched immediately into the PRESSURE EQUALIZATION position again (FIG.2).

Before the injection valve is moved from the PRESSURE EQUALIZATIONposition into the LOAD position again, the piston 53 is preferably movedinto the position C. In this way, the pressure in the sample loop isbrought into line with the atmospheric pressure. During thisdecompression time, in the PRESSURE EQUALIZATION position of theinjection valve 3, the column 41 is already connected to the pump(s) 40by way of the hook-shaped form of the groove 25 in order to avoidpressure changes. The determination of the delivery travel of the piston53 from the position B to the position C can, as in the case of thecompression, be performed mathematically or by measurement andregulation of the pressure. Alternatively, the pressure may also bedetermined indirectly by way of a force measurement at the piston 53 orat the drive 55 of the piston.

After the decompression of the sample loop has been performed, the valve3 is moved into the LOAD position. Here, no damaging flows occur in theinjection valve, and also, no damage is caused to the chromatographycolumn by pressure changes. The same also applies for the compressionstep.

The piston 53 of the high-pressure-resistant sample delivery device 5can now be moved into the initial position A again. The excess amount offluid is discharged through the waste port 47. The unpressurized needle42 can thereafter be moved from the needle seat of the injection port 45to the corresponding sample flask in order to take in the next sample.

The position C during the decompression may also differ from the initialposition C before the compression. For example, if gradients (temporallycontrolled mixing ratio of the solvent) are pumped through the column,said position C at the end of the decompression may be different, as thecompressibility of the loop content may have changed.

The abovementioned control unit 60 may store predefined positions A, B,C and/or travel differences between said positions as a function ofparameters of the sampler as a whole, in particular as a function of thecompressibility of the solvent, elasticity characteristics of the sampleloop and of the sample delivery device etc. Said positions can then beassumed in controlled fashion (that is to say without regulation) or mayserve as approximate values or starting values for a regulated movement.

For the determination of the positions A, B, C and/or of the movementtravels for the piston, a switching process of the injection valve 3without compression or decompression may be performed. By means of apressure sensor, it is then possible to determine the pressure drop, andto determine from this the required travel or the respective position Bor C. The values thus determined may then be stored and used for furtherswitching processes using a compression or decompression. Acorresponding sensor may also be provided in the pump(s) 40. This isbecause such pumps for HPLC always have a pressure sensor in any casefor the regulation of the delivered solvent. The compressibility of themedium, in particular of the solvent, can also be determined by means ofthe pump(s) 40. Such pumps are for example designed as double-pistonpumps, wherein the switching from one piston to another piston issuitably controlled or regulated by means of a pressure sensor and acontrol unit so as to yield a highly constant flow rate. Since thecompressibility of the medium must be taken into consideration for thisswitching process, it is possible, from the suitable actuation of the(double-piston) pump during the switch from one piston to the other, todetermine the compressibility and supply this as information to thecontrol unit.

In the case of the automatic sampler presented, it is thus ensured thatin the adequately (high-)pressure-resistant sample delivery device,before the switching of the drawing-in part into the flow path to thechromatography column, that is to say before the switching of theinjection valve into the INJECT position, in a special intermediateposition of the injection valve, specifically the PRESSURE EQUALIZATIONposition, the pressure in the sample loop is brought into line with thepresent system pressure of the chromatography column by way ofcompression.

Furthermore, before the opening-up of the sample loop for the drawing-inof a sample volume from a sample vessel, that is to say before theswitching of the injection valve into the LOAD position, it ispreferably the case that, in the same intermediate position of theinjection valve, specifically the PRESSURE EQUALIZATION position, thepressure in the sample loop is brought into line with the atmosphericpressure (decompression) through the change in volume in the sampledelivery device.

FIG. 4 shows the sampler 10 according to the invention with theinjection valve 3 in the PUMP PURGE position. In said position, thegroove 25 connects the ports 15 and 12, such that the line from port 15to the pump(s) 40, the groove 25 and the port 12 can be flushed withdrawn-in fluid from the pump(s) 40. Here, the fluid that is flushedthrough, and solvent residues, are discharged from the waste line.

FIG. 5 shows the sampler 10 according to the invention with theinjection valve 3 in the FULL PURGE position. In said position, thegroove 25 connects the ports 13 and 15, and the groove 23 connects theports 16 and 12, such that the line from port 15 to the pump(s) 40, thegroove 25, the port 13, the supply part 52, the sample needle 42, theneedle seat 45, the drawing-in part 44, the sample delivery device 5,the sample loop part 51, the port 16, the groove 23 and the port 12 canbe flushed with drawn-in fluid from the pump(s) 40. Here, the fluid thatis flushed through is discharged from the waste line.

FIG. 6 shows the sampler 10 according to the invention with theinjection valve 3 in the NEGATIVE PRESSURE position. In said position,the groove 25 connects the high-pressure port 15 to the sample loop port13. Furthermore, in said position, the sample loop port 16, thehigh-pressure port 14 and the waste port 12 are not connected to anyother ports. The sample needle 42 is preferably situated in the needleseat 45, such that, by way of a pulling-out movement of the piston 53 ofthe sample delivery device 5, a negative pressure can be generated inthe sample loop 51, 44, 52, in the groove 25 that connects the ports 13and 15 to one another, and in the connecting line from port 15 to thepump(s) 40. In this way, it is possible for the hydrostatic column ofthe solvent to be overcome, and to assist the pump(s) 40 during thedrawing-in of the solvent. Furthermore, for example before the FULLPURGE or PUMP PURGE position, gas bubbles may be removed from the deviceby switching into the NEGATIVE PRESSURE position and thereby generatingthe negative pressure. This is preferably performed while the pump(s) 40are/is operating with delivery power lower than that produced by thenegative pressure of the sample delivery device, or while the pump(s)are/is in a deactivated state.

FIG. 7 shows a preferred embodiment according to the invention in whicheverything is arranged as in FIG. 5, with the only exception being thatthe line from the waste port 12 leads to a wash port of the needle seat,and the waste outflow 47 is situated at the wash port of the needle seat45. In this way, during the purging in the FULL PURGE position, thecleaning agent can be conducted into the wash port of the needle seat,and thus the sample needle 42 can also be flushed from the outside.Here, the needle is preferably moved out of the needle seat slightly,such that here, the cleaning agent can already pass into the wash portof the needle seat in order to clean the outside of the sample needle,and can subsequently be discharged from the wash port into the waste.

The following reference signs are used in FIGS. 1-7.

-   1 Stator-   2 Rotor-   3 Injection valve-   5 Sample delivery device-   10 Sampler-   12 Waste port-   13 (first) sample loop port, connected to the supply part (52)-   14 High-pressure port, connected to the chromatography column-   15 High-pressure port, connected to the high-pressure pump-   16 (second) sample loop port, connected to the sample loop part (51)-   23 Arcuate groove-   25 Hook-shaped groove-   40 Pump(s), preferably high-pressure pump(s)-   41 Chromatography column-   42 Sample needle-   43 Sample vessel-   44 Drawing-in part-   45 Injection port/needle seat-   47 Waste line-   50 Syringe-   51 Sample loop part-   52 Sample loop part or supply part-   53 Movable element-   55 Actuable drive-   V Pump volume

What is claimed is:
 1. A sampler for liquid chromatography, the samplercomprising an injection valve, the injection valve includes: (a) astator, in which the stator comprises a first port, a second port, athird port, a fourth port, and a fifth port, wherein (i) the first portis configured to be connected to a pump; (ii) the second port configuredto be connected to a chromatography column; (iii) the third port isconnected to a sample loop; (iv) the fourth port is configured todischarge fluid at a low pressure to waste; and (v) a fifth port isconnected to the sample loop; (b) a rotor, in which a face surface ofthe rotor is configured to be rotated against a face surface of thestator, the rotor comprises a first groove and a second groove, in whichthe first groove is configured to connect to two of the ports, and inwhich the second groove is configured to connect to a different two ofthe ports; (c) a sample delivery device connected to the sample loop;(d) the sample loop connected to the injection valve, the sample loopincluding: (i) a first sample loop part, in which a first end of thefirst sample loop part is connected to the fifth port and a second endof the first sample loop part is connected to the sample deliverydevice; and (ii) a second sample loop part, in which a first end of thesecond sample loop part is connected to the third port and a second endof the second sample loop part is connected to the sample deliverydevice, in which the injection valve is configured to include a LOADposition, a PRESSURE EQUALIZATION position, and an INJECT position,(iii) in the LOAD position of the injection valve, the first grooveconnects the first port and the second port such that the first groovedoes not have a dead volume, and the second groove connects the thirdport and the fourth port; (iv) in the PRESSURE EQUALIZATION position ofthe injection valve, the first groove connects the first port and thesecond port such that the first groove does have the dead volume, andthe second groove does not connect the third port and the fourth port;and (v) in the INJECT position of the injection valve, the first grooveconnects the first port and the fifth port such that the first groovedoes not have the dead volume, and the second groove connects the secondport and the third port.
 2. The sampler of claim 1, in which the secondsample loop part is configured to be in a divided state where the secondsample loop part is divided into a drawing-in part and a supply part, inwhich the drawing-in part is connected to the sample delivery device,and in the divided state, an end of the drawing-in part is configured todraw in a sample fluid, in which the second sample loop part is alsoconfigured to be in a connected state where the drawing-in part and thesupply part are connected, in the connected state, the supply part isconfigured to supply the sample fluid in a direction of the secondsample loop port; and
 3. The sampler of claim 1 further comprising: (e)the pump connected to the first port; and (f) the chromatography columnconnected to the second port.
 4. The sampler of claim 1, in which theinjection valve is also configured to include additional positions, theadditional positions selected from the group consisting of (vi) a FULLPURGE position, in which the fifth port is connected to the fourth portvia the second groove, and the first port is connected to the third portvia the first groove, (vii) a PUMP PURGE position, in which the firstport is connected to the fourth port via the first groove, and (viii) aNEGATIVE PRESSURE position in which the first port is connected to thethird port via the first groove, and the fifth port is sealingly closed.5. The sampler as claimed in claim 4, wherein, in the FULL PURGEposition, the second port is sealingly closed, and, in the PUMP PURGEposition, the third port is sealingly closed and the fifth port isconnected to the second port.
 6. The sampler as claimed in claim 1,wherein the stator consists of the first port, the second port, thethird port, the fourth port, and the fifth port.
 7. The sampler asclaimed in claim 1, in which in the PRESSURE EQUALIZATION position, thethird port and the fifth port both do not have a connection to either ofthe first port or the second port, and the first port and the secondport are connected to one another via the first groove.
 8. The sampleras claimed in claim 4, wherein the injection valve has at most sixdifferent switching positions, in which the six different switchingpositions consist of the LOAD position, the PRESSURE EQUALIZATIONposition, the INJECT position, the PUMP PURGE position, the FULL PURGEposition, and the NEGATIVE PRESSURE position.
 9. The sampler as claimedin claim 1, wherein the first port is spaced apart from the second port,from the third port, from the fourth port, and from the fifth port by ineach case a substantially same distance.
 10. The sampler as claimed inclaim 1, wherein the third port and the fifth port are situated onopposite sides with respect to the first port, and the third port andthe fifth port are both spaced apart from the fourth port and from thesecond port by in each case a substantially same distance.
 11. Thesampler as claimed in claim 10, wherein the first groove is of ahook-shaped form and the second groove is of an arcuate form.
 12. Thesampler as claimed in claim 11, wherein the rotor has at most twogrooves, in which the two grooves consist of the first groove and thesecond groove.
 13. The sampler as claimed in claim 1 further comprisinga control unit configured to actuate the injection valve and the sampledelivery device.
 14. The sampler as claimed in claim 13, wherein thesample delivery device includes a movable element, the movable elementis guided in a sealed fashion in a pump volume of the sample deliverydevice, in which the sampler further comprises a drive, the driveconfigured to move the movable element, the control unit configured toactuate the drive and deliver the sample fluid contained in the pumpvolume.
 15. The sampler as claimed in claim 1, wherein the sampledelivery device is configured to generate pressure ranging from 500 barto 1500 bar.
 16. The sampler as claimed in claim 11, wherein thehook-shaped form is configured maintain a connection between the secondport and the first port during a change from the LOAD position to thePRESSURE EQUALIZATION position.